doc/tutorial/broadcasting.txt has been modified so it doesn't generate an error…

doc/tutorial/broadcasting.txt

@@ -34,6 +34,9 @@ information is given in the :ref:`type` of a *Variable*.
 
 The following code illustrates how rows and columns are broadcasted in order to perform an addition operation with a matrix:
 
+>>> import numpy as np
+>>> import theano
+>>> import theano.tensor as T
 >>> r = T.row()
 >>> r.broadcastable
 (True, False)